1. Field of the Invention
The present invention relates to a package having a facility for performing mutual conversion among different kinds of signaling signals and further relates to a time-division multiplexer equipped with the package and a speech handling network using the time-division multiplexer.
When a speech handling network is constructed among a large number of subscribers, one exchange and another exchange for respectively accommodating one group of subscribers and another group of subscribers are employed and are connected by dedicated lines. In order to transfer transmission signals onto the dedicated lines with a high efficiency, time-division multiplexers are respectively provided in the exchanges. The transmission signals are transferred on the dedicated lines via these time-division multiplexers.
Each of the transmission signals is composed of the original speech data to be transmitted and signaling signals for controlling the transmission and reception of the speech data between the above exchanges. These speech data and signaling signals are transferred onto the dedicated lines under a time-division multiplex mode.
Looking here at the signaling signals, the signaling signal is generated according to a signaling system determined in advance by the communication standard used etc. As such a signaling system, there are the T.1 signaling system, T.6 signaling system, SS/SR signaling system, etc. The system differs for every country or region in many cases.
Accordingly, where constructing the above speech handling network, if the plurality of the exchanges are located not only in a single country or region, but are also located dispersed in other countries or areas, the signaling signals will be handled under different signaling systems. Therefore the differences of the signaling systems must be absorbed in some way or another.
The present invention relates to the techniques for promoting common use of such different kinds of signaling signals.
2. Description of the Related Art
As will be explained in detail later by using the drawings, assume that a speech handling network based on a signaling system I has been constructed in Japan and that it has become necessary to expand the speech handling network to overseas subscribers. In this case, it is necessary to construct an additional one or more offices abroad too. In constructing additional offices, the signaling system I on which the speech handling network is based and a signaling system II used as the standard of the overseas offices additionally constructed will no longer match, therefore it will not be possible to use the originally used repeater exchanges II of the overseas standard. This is because, the repeater exchange I and the repeater exchanges II have different signaling systems from each other, therefore they cannot communicate with each other as they are.
As a result, in a conventional speech handling network, time-division multiplexers  less than 2 greater than ,  less than 3 greater than , and  less than 4 greater than , mentioned later, to be additionally installed overseas are constituted by using an interface panel (TTC-2M interface) currently used in the time-division multiplexer  less than 1 greater than , also mentioned later, actually used in Japan. In keeping with this, in the repeater exchanges, it is necessary to go to the trouble of replacing the repeater exchanges II of the overseas standard by repeater exchanges I of the Japanese standard. This means that the capital investment of new exchanges must be made in the additional installation of an office B and office C mentioned later regardless of the fact that there are already existing exchanges. This causes a problem in that it is uneconomical for the overseas users.
Accordingly, in consideration with the above problem, an object of the present invention is to enable the easy construction of a speech handling network capable of handling a mixture of different kinds of signaling systems by just adding extremely simple hardware to the time-division multiplexers and to provide a package having a facility for mutual conversion among different kinds of signaling signals, a time-division multiplexer including this package, and a speech handling network built by using the time-division multiplexer.
To attain the above object, the present invention provides a package for performing mutual conversion between a first signaling signal and a second signaling signal. This package comprises a first signaling signal converting means for outputting mutually converted first and second signaling signals and outputting current state information based on preceding state information and current first and second signaling signals; a second signaling state holding means for holding the current state information up to the next frame; and a timer means for detecting an appearance of current state information matching predetermined state information and outputting a time-out signal after an elapse of a predetermined time. Further, a time-division multiplexer is realized by including this package.